The invention relates generally to the manufacture and repair of components having fluid flow passages. More particularly, the invention relates to a brazing procedure for sealing leaks in fluid flow passages in components of turbomachines such as nozzles.
In the design of gas turbine engines, fluid flow through the engine is varied by a plurality of stator vanes and rotor blades. Typically, static nozzle segments direct the flow of a working fluid into stages of turbine blades connected to a rotating rotor. Each nozzle has an airfoil or vane shape configured such that when a set of nozzles are positioned about a rotor of the turbine, they direct the gas flow in an optimal direction and with an optimal pressure against the rotor blades. These vanes typically include cooling passages to prevent overheating and subsequent deforming of the component.
Fabrication of components such as nozzles, particularly using single-crystal materials to withstand higher temperatures, is a cost-intensive endeavor. Once in fully fabricated form, the nozzle may be subjected to hydrotesting to confirm its air- and water-tightness before being installed in a turbomachine. Occasionally, a leak may be found during hydrotesting. One potential solution to address such a leak may be to weld it closed. However, welding may not provide a solution in cases where the leak is not directly accessible, or the weldability of the base material of the component is poor. Another solution has been to use brazing repair methods using a liquid braze filler material. However, a liquid braze filler relies on capillary forces to draw the filler material into the gap causing the leak. Capillary forces cannot be relied upon when the interior surfaces of the component are not completely clean and free of particulate matter.